Habitat and Ecology

Habitat and Ecology

In one study, small post-settlement humphead wrasses were found in a species of seagrass (Enhalys acoroides), four species of hard coral (three Acropora spp. and Porites cylindricus), and in the soft coral Sarcophyton sp. (branching form; M.A. Tupper, pers. comm.). After settlement, juveniles and adults live associated with reef or near-reef habitats of seagrass beds and mangrove areas, with juveniles typically inshore and the largest individuals found in deeper waters of outer reefs or lagoons (Myers 1999). Juveniles of 3â20 cm TL, and larger, occur in coral-rich areas of lagoon reefs, particularly among live thickets of staghorn, Acropora spp. corals, in seagrass beds, murky outer river areas with patch reefs, shallow sandy areas adjacent to coral reef lagoons, and mangrove and seagrass areas inshore (Randall 1955, Randallet al. 1978, Myers 1999, J.H. Choat, pers. comm.). Recruitment patterns may vary considerably between years (M.A. Tupper, unpublished data). Adults are more common offshore than inshore, their presumed preferred habitat being steep outer reef slopes, reef drop-offs, reef tops, channel slopes, reef passes, and lagoon reefs to at least 100 m. They are usually found in association with well-developed coral reefs (Vivien 1973, Randall et all. 1978, Winterbottom et al. 1989, Allen and Swainston 1992, Sluka 2000). Typically they are solitary or paired, but have also been noted in groups of 3â7 individuals (Donaldson 1995). They appear to be somewhat sedentary in that the same individuals, indentifiable by distinct natural markings, may be seen along the same stretch of reef for extended periods. Indeed, many commercial dive sites have their âresidentâ Humphead Wrasse, a favoured species for divers. Natural densities are evidently never high, even in presumed preferred habitats. For example, in unfished or lightly fished areas, densities may range from two to rarely more than 10â20 individuals per 10,000 mÂ² of suitable reef. In fished areas, however, densities are typically lower by tenfold or more, and in some places fish no longer appear to be present.

Accounts of reproductive activity in the field reveal that, depending on location, this species spawns between several and all months of the year, in small or large groupings, that spawning coincides with certain phases of the tidal cycle, and that groups of spawning fish can form daily, at a range of different reef types. Spawning areas and aggregated adults have been noted regularly along specific sections of reef, sometimes associated with no obvious topographical features, sometimes close to the shelf edge on outer reefs, or adjacent to exposed reef passes near fairly steep drop-offs, or on mid-shelf (unspecified) reefs (P.L. Colin, J.H. Choat, R. Hamilton, S. Oakley, pers. comms.). The species is evidently a daily spawner that probably does not migrate far to its spawning site(s), spawning for extended periods each year, i.e., a âresidentâ spawner (Domeier and Colin 1997, P.L. Colin, pers. comm.): groups of up to 150 fish were observed in Palau along the shelf edge in a loose aggregation.

Probable spawning aggregations have also been noted on Australiaâs Great Barrier Reef (GBR), Fiji, New Caledonia, and in the Solomon Islands. Although spawning was not always observed, aggregated fish were ripe, or exhibiting behaviour likely associated with spawning. On the GBR, aggregations of up to 10 large males and 20â50 smaller fish (35â95 cm TL) were noted (J.H. Choat, pers. comm.). GBR aggregations from the Ribbon Reefs and north of Jewell Reef, once noted to include hundreds of fish, are no longer known at the same sites (Johannes and Squire 1988, L. Squire, pers. comm.).

The longevity of this species is up to at least 32 years, with females outliving the males (the oldest female recorded was 32 years), and sexual maturity is reached at about eight years of age (Choat in Pogonosky et al. 2002). Histological studies show that sexual maturation is reached at a size of between 40 cm and 60 cm total length (Sadovy, unpublished data). This species is thought to be a protogynous hermaphrodite, with sex reversal occurring at about 15 years of age (Choat in Pogonosky et al. 2002). At a total length of approximately 111 cm (Lau and Li 2000). Males grow very rapidly (Choat in Pogonosky et al. 2002).

It feeds on a variety of molluscs, fishes, sea urchins, crustaceans and other invertebrates (Randall et al. 1997).